Partial echo cancellation duplexing

ABSTRACT

Methods, circuitries, and systems for transmitting data upstream between a first device and a second device and downstream between the second device and the first device are disclosed. A method includes determining an upstream crosstalk effect for an upstream channel and determining a downstream crosstalk effect for a downstream channel. The crosstalk effect includes near end crosstalk from a third device that is non-co-located with respect to the first device and the second device. A data rate of an upstream transmission or downstream transmission is adjusted based on the upstream crosstalk effect and the downstream crosstalk effect.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a National Phase entry application of InternationalPatent Application No. PCT/US2018/012290 filed on Jan. 4, 2018, whichclaims priority to U.S. Provisional Patent Application Ser. No.62/469,850, filed on Mar. 10, 2017, entitled “PARTIAL ECHO CANCELLATIONDUPLEXING FOR MULTI-USER ACCESS OVER CABLE BINDERS” in the name ofRainer Strobel et al. and is hereby incorporated by reference in itsentirety.

BACKGROUND

Increase of the data rate is an important goal in communication systems.Full duplex transmission, using the same transmit time and frequency forupstream and downstream transmission, and applying echo cancellation isone method to increase data rates, especially for cases where asymmetric upstream/downstream ratio and low latencies are required. Inecho cancellation, a model of the echo path is created and used toestimate an echo for a signal being transmitted. This estimated echo isthen subtracted from the received signal to increase the signal-to-noiseratio.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example multi-user twisted pair network with twoindependent non-co-located users.

FIG. 2 illustrates an example partial echo cancellation system thatsupports transmission using partial echo cancellation duplexing inaccordance with various aspects described.

FIG. 3 illustrates examples of probe sequences that may be generated bythe system of FIG. 2 to determine crosstalk effects and to performchannel estimation in accordance with various aspects described.

FIG. 4 illustrates additional examples of probe sequences that may begenerated by the system of FIG. 2 to determine crosstalk effects and toperform channel estimation in accordance with various aspects described.

FIGS. 5A-5C illustrate example frames constructed to perform varioustypes of duplexing in accordance with various aspects described.

FIG. 6A illustrates data rate regions for various types of duplexing.

FIG. 6B illustrates an example frame constructed to perform partial timedivision and frequency division echo cancellation duplexing inaccordance with various aspects described.

FIG. 7 illustrates a flow diagram of an example method for performingpartial echo cancellation duplexing in accordance with various aspectsdescribed.

FIGS. 8A-8E illustrate frame formats that may be used in variousaspects.

DESCRIPTION

The present disclosure will now be described with reference to theattached figures, wherein like reference numerals are used to refer tolike elements throughout, and wherein the illustrated structures anddevices are not necessarily drawn to scale. As utilized herein, terms“module”, “component,” “system,” “circuit,” “element,” “slice,”“circuitry,” and the like are intended to refer to a computer-relatedentity, hardware, software (e.g., in execution), and/or firmware. Forexample, circuitry or a similar term can be a processor, a processrunning on a processor, a controller, an object, an executable program,a storage device, and/or a computer with a processing device. By way ofillustration, an application running on a server and the server can alsobe circuitry. One or more circuits can reside within the same circuitry,and circuitry can be localized on one computer and/or distributedbetween two or more computers. A set of elements or a set of othercircuits can be described herein, in which the term “set” can beinterpreted as “one or more.”

As another example, circuitry or similar term can be an apparatus withspecific functionality provided by mechanical parts operated by electricor electronic circuitry, in which the electric or electronic circuitrycan be operated by a software application or a firmware applicationexecuted by one or more processors. The one or more processors can beinternal or external to the apparatus and can execute at least a part ofthe software or firmware application. As yet another example, circuitrycan be an apparatus that provides specific functionality throughelectronic components without mechanical parts; the electroniccomponents can include one or more processors therein to executesoftware and/or firmware that confer(s), at least in part, thefunctionality of the electronic components.

It will be understood that when an element is referred to as being“electrically connected” or “electrically coupled” to another element,it can be physically connected or coupled to the other element such thatcurrent and/or electromagnetic radiation can flow along a conductivepath formed by the elements. Intervening conductive, inductive, orcapacitive elements may be present between the element and the otherelement when the elements are described as being electrically coupled orconnected to one another. Further, when electrically coupled orconnected to one another, one element may be capable of inducing avoltage or current flow or propagation of an electro-magnetic wave inthe other element without physical contact or intervening components.Further, when a voltage, current, or signal is referred to as being“applied” to an element, the voltage, current, or signal may beconducted to the element by way of a physical connection or by way ofcapacitive, electro-magnetic, or inductive coupling that does notinvolve a physical connection.

Use of the word exemplary is intended to present concepts in a concretefashion. The terminology used herein is for the purpose of describingparticular examples only and is not intended to be limiting of examples.As used herein, the singular forms “a,” “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises,”“comprising,” “includes” and/or “including,” when used herein, specifythe presence of stated features, integers, steps, operations, elementsand/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components and/or groups thereof.

In the following description, a plurality of details is set forth toprovide a more thorough explanation of the embodiments of the presentdisclosure. However, it will be apparent to one skilled in the art thatembodiments of the present disclosure may be practiced without thesespecific details. In other instances, well-known structures and devicesare shown in block diagram form rather than in detail in order to avoidobscuring embodiments of the present disclosure. In addition, featuresof the different embodiments described hereinafter may be combined witheach other, unless specifically noted otherwise.

A phone line network often consists of cable binders with multipletwisted pairs, serving multiple subscribers. In multi-pair bindersnear-end crosstalk (NEXT) between different subscribers is present bothat the distribution point (DPU) and at the customer premises equipment(CPE) end. Echo cancellation is usually feasible at both the DPU and theCPE end of the line because the transmit signal is known to the localreceiver. However, this not necessarily the case for NEXT. At the DPU,where all the lines are co-located, NEXT sources are usually known tolocal receivers, but at the CPE side NEXT signals may come from aneighboring, non-co-located CPE.

On a single line full duplex can be used as limited by line attenuationor depth of echo cancellation. In point-to-point MIMO, the NEXT betweenthe transmitters and receivers of different lines can be cancelled inaddition to echo cancellation because all transmit signals are availableto the receiver at the same physical location.

In a multi-subscriber case, NEXT can be cancelled at the DPU, but can'tbe cancelled between CPEs since the CPEs are not co-located, whichsubstantially limits the downstream data rates for full duplex.Therefore, full duplex in multi-subscriber lines is currently onlypossible for cases in which NEXT is weak, which happens at very lowfrequencies or in very specific deployment scenarios. Neither of thesecases are applicable for generic high-speed access networks over twistedpairs or similar metallic access.

Current G.fast systems use time division duplexing (TDD) to separateupstream and downstream transmission in time to eliminate NEXT. LegacyxDSL systems apply echo cancellation (e.g., HDSL or SHDSL) and operateat rather low frequencies where NEXT is relatively small andcancellation of echo is sufficient.

High frequency full duplex transmission systems such as Gigabit Ethernet(IEEE 1GBaseT standard) and 10 Gigabit Ethernet (IEEE 10GBaseT standard)use co-located transceivers with MIMO techniques to avoid self-NEXT anduse special shielded cables to avoid NEXT from other cables of themulti-user cable bundle. Multi-user detection has also been used toaddress NEXT in multi-user scenarios. However, this solution is highlycomplex and suffers from accuracy problems. Thus, there are nosatisfactory current solutions providing full duplex operation for linesdeployed in a generic multi-user cable binder (i.e., cable bindersserving non co-located users).

FIG. 1 illustrates an example of a multi-user twisted pair network 100with two independent non-co-located subscribers (i.e., CPE). In theexample, each CPE is connected to a DPU using two pairs of wires. Thetwo pairs of wires per CPE embody a 2-pair bonding solution, to increasethe data rate. In this case, full NEXT cancellation is only possible atthe DPU side, where all transmit and receive signals are co-located.Similarly, NEXT at the CPE side could be cancelled between two pairsconnecting each CPE. However, the CPE does not know the transmit signalof the other CPE and therefore NEXT between the two CPEs cannot becancelled. At high frequencies, NEXT between the CPEs becomes thedominant disturber of the downstream and thus full duplex transmissionbecomes inefficient for certain frequencies. Therefore it is importantto mitigate, as much as possible, the signal-to-noise ratio (SNR)degradation caused by NEXT from non-co-located CPEs. Far end crosstalk(FEXT) that occurs between lines of both co-located and non-co-locatedCPEs can be cancelled using vectoring techniques employed in G.fast orvectored VDSL2 (as per ITU-T G.993.5).

Described herein are techniques that allow estimation of the crosstalkeffects in the upstream and downstream channels between independentnon-co-located subscribers when the line is initiated. These estimationsare updated during routine transmission and reception of data frames(often called “showtime”). Further, based on the obtained estimations,partial echo cancellation (EC) may be performed in which transmissiontimes and/or transmission powers in different lines are adjusted on aper frequency basis in upstream and downstream transmission directionsso that the impact of NEXT is substantially reduced. The amount ofoverlap in time and frequency during partial EC operation can be tunedto maximize data rate for every particular channel condition for anygiven performance optimization criteria.

The described systems, methods, and circuitries allow multi-user fullduplex transmission using echo cancellation, even in scenarios when NEXTcan't be cancelled due to a lack of knowledge of the disturbing signal.The invention identifies transmit times, frequencies, and transmitsignal levels that allow efficient use of echo cancellation. For partsof the transmission time and the transmit spectrum in which simultaneousupstream and downstream transmission is not feasible, NEXT or echo orboth are avoided (by use of TDD or FDD duplexing).

FIG. 2 illustrates an example partial echo cancellation duplexing system200 that adjusts the data rate of transmissions using partial echocancellation techniques. In one example, the system 200 is implementedin a DPU, and controls transceivers in the DPU as well as in the CPEs.The system 200 includes channel evaluation circuitry 210 and partialecho cancellation circuitry 220. The channel evaluation circuitry 210 isconfigured to determine crosstalk effects such as SNR, and/or NEXT echocoupling, and/or FEXT echo coupling for the upstream and downstreamchannels in a manner that takes into account NEXT and/or FEXT fromnon-co-located devices. The partial echo cancellation circuitry 220 isconfigured to use partial echo cancellation to, when necessary, adjustthe data rate to compensate for the NEXT and/or FEXT.

The partial echo cancellation circuitry 220 includes data ratecalculation circuitry 230, mode selection circuitry 240, and frameconstruction circuitry 250. The data rate calculation circuitry 230 isconfigured to calculate an upstream (US) data rate R_(US) and adownstream (DS) data rate R_(DS) based on the crosstalk effectsdetermined by the channel evaluation circuitry 210. The mode selectioncircuitry 240 is configured to select a full echo cancellation duplexingmode or partial echo cancellation duplexing mode based on target datarates. The frame construction circuitry 250 is configured to control theconstruction and transmission of upstream and downstream data frames toimplement the selected echo cancellation duplexing mode.

FIGS. 3 and 4 illustrate two examples of probe frames that may begenerated by a channel evaluation circuitry 310, 410, respectively, todetermine crosstalk effects. The crosstalk effects are determined basedon the knowledge of the channel, which includes the direct channel, andcrosstalk channels (FEXT and NEXT). Estimation of direct and FEXTchannels for multi-line cable binders and non-co-located CPEs is widelyused in the existing systems, such as vectored VDSL2 (ITU-T G.993.5) andG.fast (ITU-T G.9701). Estimation of NEXT between lines with co-locatedinputs and outputs is also well known in MIMO techniques. However, notechniques are known to estimate NEXT from a non-co-located CPE, whichis a key problem in full duplex operation in a multi-user environment.

FIG. 3 illustrates a NEXT and FEXT evaluation technique in which thechannel evaluation circuitry 310 generates aligned probe symbols forjoint NEXT/FEXT Evaluation. In the case of full duplex, NEXT and FEXTevaluation can be done jointly. For this the channel evaluationcircuitry 310 generates DS and US symbols carrying probe sequences thatare aligned in time. In the illustrated probe sequences, seven symbol“positions” are depicted. Each position either carries a data symbol(“D”), a SYNC symbol, or is a quiet position (Q). For the purposes ofthis description, a quiet position and a blank or empty symbol in theframe are to be considered as the same.

Referring now to FIG. 3, a first set of probe sequences 330 and a secondset of sequences 340 are shown. In both sets, a joining line during itstraining uses time division duplexing (TDD) to avoid echo, until theecho canceler is sufficiently trained as shown in the trainingsequences. The symbol positions filled with training symbols are denoted“T.”

To identify NEXT and FEXT channels from multiple lines, specialpre-defined sequences (further called “probe sequences”, which areusually mutually orthogonal, such as Walsh-Hadamard sequences, orpseudo-orthogonal, such as M-sequences) are transmitted by each CPE onall relevant tones of the pre-defined upstream symbols and by the DPU onpre-defined downstream symbols (SYNC symbols in FIGS. 3 and 4). Allupstream SYNC symbol positions of all lines are mutually aligned intime. All downstream SYNC symbol positions are also mutually aligned intime. To accommodate different delays in different lines, appropriatecyclic extension may be applied. In one example, instead of two SYNCsymbol positions per frame, a single SYNC symbol position is used perframe to estimate both upstream and downstream NEXT and/or FEXT.

The channel estimation circuitry 310 estimates the channel on all tonesused for transmission or on a subset of tones. In case of channelestimation on a subset of tones, the channel estimation for intermediatetones is derived from the estimated tones, e.g., by interpolation. Inestimating the channel, the channel estimation circuitry 310 determinescrosstalk effects such as SNR, and/or NEXT echo coupling, and/or FEXTecho coupling for the upstream and downstream channels in a manner thattakes into account NEXT and/or FEXT from non-co-located devices.

FIG. 3 shows an example of a joining line operating in TDD mode (duringrelevant part of its training) and an “operation” line (i.e., during“showtime” as opposed to training) operating in full duplex. Twoapproaches are shown in FIG. 3. The set of sequences 330 shows the casein which downstream SYNC symbols in a first symbol position 332 and theupstream SYNC symbols in a second symbol position 337 are aligned intime, and all lines transmit probe sequences over SYNC symbols in bothupstream and downstream directions. As upstream and downstream sequencesare mutually orthogonal, all crosstalk channels (FEXT in upstream anddownstream and NEXT in upstream and downstream) can be estimated. Duringthe first SYNC position 332, downstream channel SNR is measured anddownstream channel FEXT and downstream channel NEXT (DPU side) areestimated by the channel estimation circuitry 310. Echo estimation isalso performed during the first SYNC position 332. During the secondSYNC position 337, upstream channel SNR is measured and upstream FEXTand NEXT (CPE side) are estimated by the channel estimation circuitry310. Echo estimation is also performed during the second SYNC position337.

In the example shown in the set of sequences 340 the downstream SYNCsymbol transmission during the second NEXT channel estimation symbolposition 347 (NEXT-TS) is stopped in both joining and showtime lines(quiet periods are assigned) to avoid a downstream FEXT component beingpresent in the NEXT estimation. This can be achieved by sending a quietdownstream SYNC symbol (without probe sequence or with a probe sequencecontaining only zero-power (Z) elements) at the same position as anupstream SYNC symbol. Analogously, a quiet symbol is sent upstream whilea SYNC symbol is sent downstream in symbol position 342. During thefirst SYNC position 342, downstream channel SNR is measured anddownstream channel FEXT and downstream channel NEXT (DPU side) areestimated by the channel estimation circuitry 310. Echo estimation isalso performed during the first SYNC position 342. During the secondSYNC position 347, upstream channel SNR is measured and upstream FEXTand NEXT (CPE side) are estimated by the channel estimation circuitry310. Echo estimation is also performed during the second SYNC position347.

In one example, to estimate the NEXT and FEXT the DPU collects errorsignals after one or more repetitions of the probe sequencetransmission, while the transmit PSD of the subcarriers of the SYNCsymbol is unchanged. The DPU indicates to the CPEs via the DS managementchannel when the sufficient number of probe sequence cycles iscollected. Further, the DPU can start downstream transmission of (dataor management information) in the previously released NEXT-TS positions.

In another example, the DPU may use a joint iterative process forFEXT/NEXT estimation which includes adaptation of the transmit power ofthe subcarriers in both the upstream and downstream SYNC symbols. Afterreceiving a set of error signals from all CPEs, the DPU communicates toeach CPE via the downstream management channel what transmit powershould be set to each subcarrier of the upstream SYNC symbols for thenext set of reported error signals. Further, the DPU updates thetransmit power of the subcarriers in downstream SYNC symbols and CPEsupdate the power of the subcarriers in the upstream SYNC symbols, sothat next set of error signals is obtained with modified transmit powersin both directions. The process converges when DPU concludes thatsufficient number of iterations was already performed. LMS algorithm isone typical type of iterative process.

In another example, the probe sequences carry random values (such asPRBS or user data) and DPU runs an iterative process updating thetransmit power of US subcarriers during SYNC symbols, as describedabove. The convergence process for this example is usually relativelyslow. In another example, the DPU transmits SYNC symbols on the NEXT-TSpositions carrying probe sequences containing only Z-elements.

In another example, downstream SYNC symbols are precoded at the DPU sideto cancel FEXT and the upstream SYNC symbols are equalized at the DPUside. In another example, downstream SYNC symbols are not precoded atthe DPU side and upstream SYNC symbols are not equalized at the DPUside, such that the SYNC symbols experience the full FEXT.

In another example, NEXT and echo are cancelled during the SYNC symbolsand only the residual NEXT and echo are estimated. This can be used inupstream as well as in downstream direction (in case NEXT is from aco-located transceiver), e.g., to run adaptive algorithms for NEXTcanceler training. In another example, NEXT and echo are not cancelledduring the SYNC symbols and the channel estimation contains full NEXTand echo. This can be used in upstream as well as in downstreamdirection, in case of an open-loop update of the NEXT and echo cancellerwith sub-sequent channel estimation and canceler calculation steps.

FIG. 4 illustrates an example channel estimation circuitry 410 thatperforms crosstalk effect evaluation without aligned probe symbols sothat FEXT and NEXT are evaluated independently. Joining lines, as inFIG. 3, start from the TDD frame format. The downstream and upstreamSYNC symbols in the first SYNC symbol position 432 are placed in theprobe sequences at different symbol positions (while downstream SYNCsymbols in all lines are mutually aligned and upstream SYNC symbols insecond SYNC position 437 in all lines are mutually aligned). By usingTDD, a joining line may avoid echo until the echo canceler is trainedsufficiently accurate. In the example shown in FIG. 4, it is notrequired to select probe sequences such that upstream and downstreamprobe sequences in SYNC symbols are mutually orthogonal. Only upstreamprobe sequences of different lines should be mutually orthogonal. In theset of sequences 430, the showtime lines transmit data at the upstreamSYNC symbol positions of the training lines, which may reduce thechannel estimation quality due to NEXT from the operation lines. Duringthe first SYNC position 432, downstream channel SNR is measured anddownstream channel FEXT and downstream channel NEXT (DPU side) areestimated by the channel estimation circuitry 410. Echo estimation isalso performed during the first SYNC position 432. During the secondSYNC position 437, upstream channel SNR is measured and upstream FEXTand NEXT (CPE side) are estimated by the channel estimation circuitry410. Echo estimation is also performed during the second SYNC position437.

The quality of the channel estimation is improved in the set ofsequences 440 by transmitting quiet symbols on the showtime lines at theupstream SYNC symbol positions of the training lines. During the firstSYNC position 442, downstream channel SNR is measured and downstreamchannel FEXT and downstream channel NEXT (DPU side) are estimated by thechannel estimation circuitry 410. Echo estimation is also performedduring the first SYNC position 442. During the second SYNC position 447,upstream channel SNR is measured and upstream FEXT and NEXT (CPE side)are estimated by the channel estimation circuitry 410. Echo estimationis also performed during the second SYNC position 447.

Further, during showtime, NEXT estimation is routinely updated and theset of sequences 330 or 430 can be used. Since SYNC symbols are usuallytransmitted once during a superframe, loss of one downstream symbolposition per superframe causes insignificant performance loss. It mayalso be combined with discontinuous operation (DO) as currently definedin G.fast (G.9701).

In one example, the DPU collects error signals after one or morerepetitions of the upstream probe sequences transmission, while thetransmit PSD of the subcarriers of the upstream SYNC symbols areunchanged. The DPU indicates to the CPEs via the downstream managementchannel when the sufficient number of probe sequence cycles iscollected. In another example, the probe sequences in upstream carrypseudo-random random bit values (such as PRBS or user data) and DPU runsan iterative process updating the transmit power of US subcarriersduring SYNC symbols, as described above. The convergence process forthis example is usually relatively slow.

Now that several channel estimation techniques have been described,partial echo cancellation will be set forth in detail. The partial echocancellation techniques may be performed by the partial echocancellation circuitry 220 of FIG. 2. Recall that the data ratecalculation circuitry 230 is configured to calculate upstream anddownstream data rates in the presence of NEXT. In cases when a fulloverlap of upstream and downstream transmit time and transmit spectrum(i.e., full EC duplexing) is not optimal to achieve the highest datarate (due to impact of NEXT or inability to perfectly cancel echo), modeselection circuitry 240 may select partial echo cancellation duplexingmode. As will be described in more detail below, partial echocancellation duplexing mode may be implemented in three differentmanners. Partial echo cancellation duplexing may utilize partialfrequency overlap during selected symbol positions in a frame, partialtransmit time overlap (during selected symbol positions) in a frame, ora combination of partial time and frequency overlap. In addition,reduction in transmit power can be applied on particular subcarriers orall subcarriers during selected symbol positions in a frame.

In some examples the mode selection circuitry 240 determines specificoverlapping and non-overlapping frequencies with respect to the desiredupstream/downstream data rate ratio or a target relationship between theupstream and downstream data rates, but also with respect to the receivesignal strength and the crosstalk strength within a certain frequencyband.

In one example, the mode selection circuitry 240 selects a partialtransmit time overlap to allow for control of the ratio between upstreamand downstream data rates very efficiently by the corresponding settingof exclusive downstream transmission time, overlapped US/DS transmissiontime, and exclusive upstream transmission time. The particularallocation of the transmit time, transmit frequency spectrum, andtransmit power, different optimization objectives are possible. Forexample, the mode selection circuitry 240 may select a partial echocancellation duplexing mode that maximizes a sum-rate (US+DS) orweighted sum-rate max(ω_(us)R_(us)+ω_(ds)R_(ds)). In another example,the mode selection circuitry 240 may fix the downstream data rate andselect a partial echo cancellation duplexing mode that maximizes the USrate or fix the US rate and select a partial echo cancellation duplexingmode that maximizes the DS rate. In another example, the mode selectioncircuitry 240 selects a partial echo cancellation duplexing mode thatmaximizes a sum-rate with a given target US/DS ratio ω_(us)/ω_(ds),which corresponds to max min(

,

). The settings may be coordinated and optimized among the lines of thevectored group.

To analyze the different schemes, the channel evaluation circuitry 210determines crosstalk effects and the data rate calculation circuitry 230calculates data rates for the case of full echo cancellation based onthe determined crosstalk effects. Assuming perfect NEXT and FEXTcancellation, the upstream SNR SNR_(us,v) ^((k)) of line v and carrier kcan be calculated by the channel evaluation circuitry 210 by:

$\begin{matrix}{{SNR}_{{{us}/{ds}},{nextfree},v}^{(k)} = \frac{x_{{us},v}^{(k)}{H_{{us},{vv}}^{(k)}}^{2}}{\sigma^{2}}} & (1)\end{matrix}$where H_(us,vv) ^((k)) is the upstream direct channel of line v,x_(us,v) ^((k)) is the upstream transmit power of line v and carrier kand σ² is the receiver noise variance.

For downstream direction, the NEXT from the neighboring CPEs, connectedto the lines d∈

_(dist,v) cannot be cancelled and is considered as noise, which givesthe SNR according to:

$\begin{matrix}{{SNR}_{{ds},v}^{(k)} = \frac{x_{{ds},v}^{(k)}{H_{{ds},{vv}}^{(k)}}^{2}}{\sigma^{2} + {\Sigma_{d \in \lbrack_{{dist},v}}x_{{us},d}^{(k)}{H_{{cpenext},{vd}}^{(k)}}^{2}}}} & (2)\end{matrix}$where H_(ds,vv) ^((k)) is the downstream direct channel transferfunction of line v, x_(ds,v) ^((k)) is the downstream transmit power ofline v on carrier k, and H_(cpenext,vd) ^((k)) is the NEXT coupling fromthe CPE transmitter of line d to the CPE receiver of line v.

The data rate calculation circuitry 240 calculates the data rate on linev (the downstream data rate with/without NEXT or the upstream data rate)for example, by:

$\begin{matrix}{R_{{{{ds}/{us}}/{ds}},{nextfree},v} = {\sum\limits_{k = 1}^{K}\;{\log_{2}\left( \frac{1 + {SNR}_{{{{ds}/{us}}/{nextfree}},v}^{(k)}}{\Gamma} \right)}}} & (3)\end{matrix}$where Γ accounts for the SNR gap to capacity due to QAM modulation, theused channel coding scheme, and the applied SNR margin γ_(m) (requiredas a condition for the target data error rate).

Depending on the associated standard, different duplexing schemes areused in DSL technologies. While G.fast uses TDD, VDSL2 uses FDD. In bothcases, there are dedicated management symbols, e.g., SYNC symbols, forcrosstalk channel estimation and other transmission means (e.g., specialsymbols or data units) to carry the overhead channel which is necessaryto assist channel estimation. FIGS. 5A, 5B, and 5C illustrate variousframing scenarios for different types of duplexing. FIG. 5A illustratesframing for time division duplexing (TDD). FIG. 5B illustrates framingfor full echo cancellation (EC) duplexing. FIG. 5C illustrates framingfor partial time division echo cancellation duplexing (which is alsosuitable for cases of non-co-located NEXT at the CPE side, as describedabove). The frame construction circuitry 250 (FIG. 2) constructs framescommunicating the transmit data according to a selected one of theframing scenarios.

There may be frequencies at which use of full duplex increases the sumof upstream and downstream data rate even in presence of someuncancelled NEXT (because DS SNR is still sufficiently high), while forother frequencies, the sum or weighted sum of upstream and downstreamdata rate is lower due to the NEXT (because no DS capacity left).Therefore, all framing options described above allow the use of FDDinside all or selected symbol positions. This means that during selectedsymbol positions upstream transmission occurs on a first set ofparticular channel frequencies (e.g., all available channel frequencies)while downstream transmission occurs on a second, different, set oftransmission frequencies. Further, at other symbol positions, downstreamtransmission occurs on the first set of frequencies while upstreamtransmission occurs on a third, different, set of transmissionfrequencies

A simple scheme of partial echo cancellation in the frequency domain isto disable upstream transmissions for frequencies on which the weightedsum of upstream and downstream data rate (with NEXT) is less than onethat can be achieved by using TDD (i.e., when only DS or only US istransmitted), which gives, e.g.:

$\begin{matrix}{x_{us}^{(k)} = \left( \begin{matrix}p_{mask}^{(k)} & {{{{for}\mspace{14mu}\omega_{ds}b_{ds}^{(k)}} + {\omega_{us}b_{us}^{(k)}}} \geq {\omega_{ds}b_{{ds},{nextfree}}^{(k)}}} \\o & {\mspace{275mu}{otherwise}}\end{matrix} \right.} & (4)\end{matrix}$where b^((k)) is the bit allocation

$\begin{matrix}{b_{{{{ds}/{us}}/{ds}},{nextfree},v}^{(k)} = {\log_{2}\left( \frac{1 + {SNR}_{{{{ds}/{us}}/{nextfree}},v}^{(k)}}{\Gamma} \right)}} & (5)\end{matrix}$

To further increase the benefits of partial EC duplexing, instead of ahard decision to enable or disable certain subcarriers for full duplextransmission, the mode selection circuitry 240 may control a transmittertransmitting the frames such that the transmit PSD or power level onthese subcarriers is reduced, leaving some channel capacity available,but substantially reducing the harm to the opposite transmissiondirection. Further, mode selection circuitry 240 may instructtransmitter components at the other end of the line that the transmitPSD of the corresponding subcarriers in the opposite direction beincreased, providing even higher bit rates. This way transmit spectrumin both upstream and downstream can be optimized, allowing formaximization of the data rate in both transmission directions based onthe selected optimization criterion (e.g., maximizing the US+DS datarates or providing a data rate in each direction that is above certaintarget, etc.) by using intermediate transmit power values. Whileoptimization criteria and algorithms can be different, the goal of themode selection circuitry 240 is to select an optimum partial ECduplexing mode and/or PSD level, providing the best result based onselected criteria.

The mentioned transmit spectrum optimization is based on the data rateobjective and the power constraint which should be satisfied for datatransmission on twisted pair lines. There are usually two transmit powerconstraints applied: a per-line spectral mask constraintdiag(P _(ds/us) ^((k))diag(x _(ds/us) ^((k)))P _(ds/us) ^((k),H))≤p_(mask) ^((k)) ∀k=1, . . . ,K  (6)and a per-line sum-power constraintΣ_(k=1) ^(K) diag(P _(ds/us) ^((k))diag(x _(ds/us) ^((k)))P _(ds/us)^((k),H))≤p _(sum).  (7)where the vector p_(mask) ^((k)) collects the power limits from thespectral mask at carrier k for all lines and p_(sum) is the vector ofsum-power limits. x_(ds/us) ^((k)) is the downstream or upstream powervector at precoder input.

Maximizing the weighted sum of upstream and downstream data rate andsolving for the optimum power allocation results in differentupstream/downstream ratios, which form an optimum rate region. Forexample, the weighted sum of upstream and downstream data rates may beset according to a criterion:

$\begin{matrix}{{\begin{matrix}\max \\{x_{{ds},v^{\prime}}^{(k)}x_{{us},v^{\prime}}^{(k)}}\end{matrix}{\forall k}},{{v\mspace{14mu}\omega_{ds}\mspace{14mu}{\sum\limits_{v = 1}^{L}\;{\sum\limits_{k = 1}^{K}\;{\log_{2}\left( {1 + \frac{x_{{ds},v}^{(k)}{H_{{ds},{vv}}^{(k)}}^{2}}{\sigma^{2} + {\Sigma_{d \in \lbrack_{{dist},v}}x_{{us},d}^{(k)}{H_{{cpenext},{vd}}^{(k)}}^{2}}}} \right)}}}} + {\omega_{us}{\sum\limits_{v = 1}^{L}\;{\sum\limits_{k = 1}^{K}\;{\log_{2}\left( {1 + \frac{x_{{us},v}^{(k)}{H_{{us},{vv}}^{(k)}}^{2}}{{\Gamma\sigma}^{2}}} \right)}}}}}} & (8)\end{matrix}$that is maximized, taking the un-cancelled CPE NEXT into account. Theoptimization problem may be solved by a gradient step towards increasingdata rates according to:

$\begin{matrix}{{\frac{\partial{L\left( {x_{{ds},l}^{(k)},x_{{us},l}^{(k)}} \right)}}{\partial x_{{us},l}^{(k)}} = {{\Sigma_{v \in \lbrack_{{vict},l}}\left( {\frac{{H_{{cpenext},{vl}}^{(k)}}^{2}}{\sigma^{2} + {\Sigma_{d \in \lbrack_{{dist},v}}x_{{us},d}^{(k)}{H_{{cpenext},{vd}}^{(k)}}^{2}}} - \frac{{H_{{cpenext},{vl}}^{(k)}}^{2}}{{\frac{1}{\Gamma}x_{{ds},v}^{(k)}{H_{{ds},{vv}}^{(k)}}^{2}} + \sigma^{2} + {\Sigma_{d \in \lbrack_{{dist},v}}x_{{us},d}^{(k)}{H_{{cpenext},{vd}}^{(k)}}^{2}}}} \right)} - \frac{1}{x_{{us},l}^{(k)} + \frac{{\Gamma\sigma}^{2}}{{H_{{us},{vv}}^{(k)}}^{2}}}}},} & (9)\end{matrix}$where the channel estimation of the un-cancelled CPE NEXT paths isrequired.

Without the spectrum optimization, with full duplex used during theentire frame, only one data rate point with high upstream and lowdownstream rate can be reached. Spectrum optimization with differentweights for upstream and downstream allows obtaining more symmetricrates and further increases the sum of upstream and downstream datarates (the selected optimization criterion).

Partial FD/EC duplexing, as just described, potentially achieves higheraggregated (US+DS) data rates than partial TD/EC duplexing, as shown inFIG. 6A. A generic data rate region for multi-user partial EC is shownin FIG. 6A for illustration. TDD systems switch between upstream anddownstream transmission and thereby, achieve a certain combination ofupstream and downstream rates as indicated by the line denoted as “TDD”.With partial TD/EC duplexing, the downstream transmission continuesduring the upstream time positions and the data rates as indicated bythe line “Partial TD EC duplexing,” are feasible, which are alwayshigher than the TDD rates, while the rate gain increases when higherupstream rates are requested. The use of partial FD/EC duplexing withspectrum optimization allows the data rate to reach any point on thedashed rate region. Due to un-cancelled NEXT, the rate region of partialFD/EC duplexing is not necessarily convex. Besides that, changes ofupstream/downstream data rate ratio require to re-do the spectrumoptimization, which takes time and does not allow fast switching betweendifferent upstream/downstream data rate ratios.

To combine the advantages of both, partial TD/EC duplexing and partialFD/EC duplexing, a frame format as shown in FIG. 6B can be used by theframe construction circuitry 250 to implement partial TD/EC duplexingmode and partial FD/EC duplexing mode plus spectrum optimization. Interms of rate regions, this corresponds to the line denoted as “PartialFD+TD EC Optimized” in FIG. 6A. The frame consists of symbols wherespectrum optimization is performed with priority for downstream andother symbols where optimization is performed with priority forupstream.

FIG. 7 illustrates a flow diagram of a method 700 for data upstreambetween a first device and a second device and downstream between thesecond device and the first device. At 710, the method includesdetermining crosstalk effects for an upstream channel. At 720, themethod includes determining crosstalk effects for a downstream channel.The upstream or downstream crosstalk effects, or both, include NEXT froma third device (or multiple devices) that is non-co-located with respectto the first device and the second device. At 730, the method includes,based on the upstream crosstalk effects and the downstream crosstalkeffects, adjusting a data rate of an upstream transmission or downstreamtransmission.

It can be seen from the foregoing description that the describedsystems, methods, and circuitries maximize the use of full duplexingusing echo cancellation (EC) duplexing in multi-user lines with NEXT.Use of full EC duplexing has advantages as compared to TDD or FDD sincefull EC duplexing allows simultaneous transmission in both directionsover same frequency spectrum, which substantially increases data rates.Depending on specific scenario and/or optimization criteria, partial ECtransmission can be achieved in which full EC is not performed in alltime positions and/or frequency bands. Optimization of frequency andtime overlap between upstream and downstream during partial EC duplexingoperation is based on actual channel conditions andupstream-to-downstream data rate ratio requirements, thereby improvingthe efficiency of full duplex communication. Use of overall PSDoptimization in upstream and downstream communication during partial ECduplexing operation on all cross-talking lines further improvesperformance.

FIGS. 8A, 8B, 8C and 8D illustrate frame formats that may be used invarious aspects. FIG. 8A illustrates a periodic frame structure 800 thatmay be used in various aspects. Frame structure 800 has a predeterminedduration and repeats in a periodic manner with a repetition intervalequal to the predetermined duration. Frame 800 is divided into two ormore subframes 805. In an aspect, subframes may be of predeterminedduration which may be unequal. In an alternative aspect, subframes maybe of a duration which is determined dynamically and varies betweensubsequent repetitions of frame 800.

FIG. 8B illustrates an aspect of a periodic frame structure usingfrequency division duplexing (FDD). In an aspect of FDD, downstreamframe structure 810 is transmitted by a DPU to one or CPE devices, andupstream frame structure 820 is transmitted by a combination of one ormore CPE devices to a DPU.

A further example of a frame structure that may be used in some aspectsis shown in FIG. 8D. In this example, frame 800 has a duration of 10 ms.Frame 800 is divided into symbol positions each of duration 0.5 ms, andnumbered from 0 to 19. Additionally, each pair of adjacent symbolpositions numbered 2i and 2i+1, where i is an integer, is referred to asa subframe. In some aspects using the frame format of FIG. 8D, eachsubframe may include a combination of one or more of downstream controlinformation, downstream data information, upstream control informationand upstream data information. The combination of information types anddirection may be selected independently for each subframe.

An example of a frame structure that may be used in some aspects isshown in FIG. 8E, illustrating downstream frame 850 and upstream frame855. According to some aspects, downstream frame 850 and upstream frame855 may have a duration of 10 ms, and upstream frame 855 may betransmitted with a timing advance 860 with respect to downstream frame850. According to some aspects, downstream frame 850 and upstream frame855 may each be divided into two or more subframes 865, which may be 1ms in duration. According to some aspects, each subframe 865 may consistof one or more symbol positions 870.

In some aspects, according to the examples of FIGS. 8D and 8E, timeintervals may be represented in units of T_(s). According to someaspects of the example illustrated in FIG. 8D, T_(s) may be defined as1/(30,720×1000) seconds. According to some aspects of FIG. 8D, a framemay be defined as having duration 30,720·T_(s), and a symbol positionmay be defined as having duration 15,360·T_(s). According to someaspects of the example illustrated in FIG. 8E, T_(s) may be defined asT _(s)=1/(Δf _(max) ·N _(f)),where Δf_(max)=480×103 and Nf=4,096. According to some aspects of theexample illustrated in FIG. 8E, the number of symbol positions may bedetermined based on a numerology parameter, which may be related to afrequency spacing between subcarriers of a multicarrier signal used fortransmission.

While the methods are illustrated and described below as a series ofacts or events, it will be appreciated that the illustrated ordering ofsuch acts or events are not to be interpreted in a limiting sense. Forexample, some acts may occur in different orders and/or concurrentlywith other acts or events apart from those illustrated and/or describedherein. In addition, not all illustrated acts may be required toimplement one or more aspects or embodiments of the disclosure herein.Also, one or more of the acts depicted herein may be carried out in oneor more separate acts and/or phases.

While the invention has been illustrated and described with respect toone or more implementations, alterations and/or modifications may bemade to the illustrated examples without departing from the spirit andscope of the appended claims. In particular regard to the variousfunctions performed by the above described components or structures(assemblies, devices, circuits, systems, etc.), the terms (including areference to a “means”) used to describe such components are intended tocorrespond, unless otherwise indicated, to any component or structurewhich performs the specified function of the described component (e.g.,that is functionally equivalent), even though not structurallyequivalent to the disclosed structure which performs the function in theherein illustrated exemplary implementations of the invention.

Examples can include subject matter such as a method, means forperforming acts or blocks of the method, at least one machine-readablemedium including instructions that, when performed by a machine causethe machine to perform acts of the method or of an apparatus or systemfor concurrent communication using multiple communication technologiesaccording to embodiments and examples described herein.

Example 1 is a partial echo cancellation duplexing system, including achannel estimation circuitry configured to determine an upstreamcrosstalk effect for an upstream channel between a first device and asecond device and determine a downstream crosstalk effect for adownstream channel between the first device and the second device. Theupstream crosstalk effect, the downstream crosstalk effect, or both,includes near end crosstalk from a third device that is non-co-locatedwith respect to the first device and the second device. The system alsoincludes a partial echo cancellation duplexing circuitry configured toadjust a data rate of an upstream transmission or downstreamtransmission based on the upstream crosstalk effect and the downstreamcrosstalk effect.

Example 2 includes the elements of example 1, including or omittingoptional elements, wherein the channel estimation circuitry isconfigured to determine the upstream crosstalk effect and determiningthe downstream crosstalk effect by: transmitting an upstream data frameand a downstream data frame, wherein one or both of the upstream dataframe and the downstream data frame include a synchronization symbol ora quiet symbol in a first symbol position; and measuring one or more ofa downstream channel SNR, an upstream channel SNR, a downstream channelfar end crosstalk coupling, an upstream channel far end crosstalkcoupling, a downstream channel near end crosstalk coupling, and anupstream channel near end crosstalk during the first symbol position.

Example 3 includes the elements of example 2, including or omittingoptional elements, wherein the channel estimation circuitry isconfigured to determine the upstream crosstalk effect and determiningthe downstream crosstalk effect by: transmitting an upstream data frameand a downstream data frame, wherein one or both of the upstream dataframe and the downstream data frame include a synchronization symbol ora quiet symbol in a first symbol position and a second symbol position;measuring one or more of a downstream channel SNR, a downstream channelfar end crosstalk coupling, and a downstream channel near end crosstalkcoupling during the first symbol position; and measuring one or more ofan upstream channel SNR, an upstream channel far end crosstalk coupling,and an upstream channel near end crosstalk coupling during the secondsymbol position.

Example 4 includes the elements of example 2, including or omittingoptional elements, wherein both the upstream data frame and thedownstream data frame include a synchronization symbol in the firstsymbol position.

Example 5 includes the elements of example 2, including or omittingoptional elements, wherein one of the upstream data frame and thedownstream data frame includes a synchronization symbol in the firstsymbol position and the other of the upstream data frame and thedownstream data frame includes a quiet symbol in the first symbolposition.

Example 6 includes the elements of examples 1-5, including or omittingoptional elements, wherein the partial echo cancellation duplexingcircuitry is configured to adjust the data rate by constructing anupstream data frame and a downstream data frame such that during a leastone symbol position the upstream data frame or the downstream data frameor both includes data encoded on fewer channel frequencies than theother symbol positions of the same upstream data frame or the downstreamdata frame or both.

Example 7 includes the elements of examples 1-5, including or omittingoptional elements, wherein the partial echo cancellation duplexingcircuitry is configured to adjust the data rate by constructing anupstream data frame and a downstream data frame such that i) during afirst symbol position the upstream data frame and the downstream dataframe both include data encoded on particular channel frequencies andii) during a second symbol position one of the upstream data frame orthe downstream data frame, but not both, do not include data encoded onthe particular channel frequencies.

Example 8 includes the elements of examples 1-5, including or omittingoptional elements, wherein the partial echo cancellation duplexingcircuitry is configured to adjust the data rate by constructing anupstream data frame and a downstream data frame such that i) during afirst symbol position the upstream data frame includes data encoded on afirst set of channel frequencies and the downstream data frame includesdata encoded on a second set of channel frequencies that is differentfrom the first set; and ii) during a second symbol position thedownstream data frame includes data encoded on the first set of channelfrequencies and the upstream data frame includes data encoded on a thirdset of channel frequencies that is different from the first set.

Example 9 includes the elements of examples 1-5, including or omittingoptional elements, wherein the partial echo cancellation duplexingcircuitry is configured to adjust the data rate by: constructing anupstream data frame and a downstream data frame and instructing atransmitter transmitting one of the upstream data frame or thedownstream data frame to transmit at a reduced power during a least onesymbol position in the data frame as compared to a power level used totransmit at other symbol positions in the same data frame.

Example 10 includes the elements of examples 1-5, including or omittingoptional elements, wherein the partial echo cancellation duplexingcircuitry is configured to adjust the data rate by: calculating anupstream data rate based on an upstream channel SNR assuming full duplextransmission; calculating a downstream data rate based on a downstreamchannel SNR assuming full duplex transmission; and adjusting the datarate based on a criteria that defines a target relationship between theupstream data rate and the downstream data rate.

Example 11 is a method to transmit data upstream between a first deviceand a second device and downstream between the second device and thefirst device, including: determining an upstream crosstalk effect for anupstream channel; determining a downstream crosstalk effect for adownstream channel; wherein the upstream crosstalk effect, thedownstream crosstalk effect, or both, includes near end crosstalk from athird device that is non-co-located with respect to the first device andthe second device; and based on the upstream crosstalk effect and thedownstream crosstalk effect, adjusting a data rate of an upstreamtransmission or downstream transmission.

Example 12 includes the elements of example 11, including or omittingoptional elements, wherein determining the upstream crosstalk effect anddetermining the downstream crosstalk effect includes: transmitting anupstream data frame and a downstream data frame, wherein one or both ofthe upstream data frame and the downstream data frame include asynchronization symbol or a quiet symbol in a first symbol position anda second symbol position; measuring one or more of a downstream channelSNR, downstream channel far end crosstalk coupling, and downstreamchannel near end crosstalk coupling during the first symbol position;and measuring one or more of an upstream channel SNR, upstream channelfar end crosstalk coupling, and upstream channel near end crosstalkcoupling during the second symbol position.

Example 13 includes the elements of example 11, including or omittingoptional elements, wherein determining the upstream crosstalk effect anddetermining the downstream crosstalk effect includes: transmitting anupstream data frame and a downstream data frame, wherein one or both ofthe upstream data frame and the downstream data frame include asynchronization symbol or a quiet symbol in a first symbol position andmeasuring one or more of a downstream channel SNR, an upstream channelSNR, a downstream channel far end crosstalk coupling, an upstreamchannel far end crosstalk coupling, a downstream channel near endcrosstalk coupling, and an upstream channel near end crosstalk duringthe first symbol position.

Example 14 includes the elements of examples 11-13, including oromitting optional elements, wherein adjusting the data rate includesconstructing an upstream data frame and a downstream data frame suchthat during a least one symbol position the upstream data frame or thedownstream data frame includes data encoded on fewer channel frequenciesthan the other of the upstream data frame or the downstream data frame.

Example 15 includes the elements of examples 11-13, including oromitting optional elements, wherein adjusting the data rate includesconstructing an upstream data frame and a downstream data frame suchthat i) during a first symbol position the upstream data frame and thedownstream data frame both include data encoded on particular channelfrequencies and ii) during a second symbol position one of the upstreamdata frame or the downstream data frame, but not both, do not includedata encoded on the particular channel frequencies.

Example 16 includes the elements of examples 11-13, including oromitting optional elements, wherein adjusting the data rate includesconstructing an upstream data frame and a downstream data frame suchthat i) during a first symbol position the upstream data frame includesdata encoded on a first set of channel frequencies and the downstreamdata frame includes data encoded on a second set of channel frequenciesthat is different from the first set; and ii) during a second symbolposition the downstream data frame includes data encoded on the firstset of channel frequencies and the upstream data frame includes dataencoded on a third set of channel frequencies that is different from thefirst set.

Example 17 includes the elements of examples 11-13, including oromitting optional elements, wherein adjusting the data rate includes:constructing an upstream data frame and a downstream data frame andinstructing a transmitter transmitting one of the upstream data frame orthe downstream data frame to transmit at a reduced power during a leastone symbol position in the data frames as compared to power used totransmit at other symbol positions in the data frames.

Example 18 includes the elements of examples 11-13, including oromitting optional elements, wherein adjusting the data rate includes:calculating an upstream data rate based on an upstream channel SNRassuming full duplex transmission; calculating a downstream data ratebased on an downstream channel SNR assuming full duplex transmission;and adjusting the data rate based on a criteria that defines a targetrelationship between the upstream data rate and the downstream datarate.

Example 19 is partial echo cancellation duplexing circuitry, including:a data rate calculation circuitry configured to calculate an upstreamdata rate and a downstream data rate based on estimated crosstalkeffects; a mode selection circuitry configured to select a full echocancellation duplexing mode or a partial echo cancellation duplexingmode based on target data rates; and a frame construction circuitryconfigured to control construction and transmission of upstream dataframes and downstream data frames based on the selected echocancellation duplexing mode.

Example 20 includes the elements of example 19, including or omittingoptional elements, wherein: the mode selection circuitry is configuredto select a partial frequency division echo cancellation duplexing modebased on the upstream data rate and the downstream data rate; and theframe construction circuitry is configured to, in response to selectionof the partial frequency division echo cancellation duplexing mode,construct an upstream data frame and a downstream data frame such thatduring a least one symbol position the upstream data frame or thedownstream data frame includes data encoded on fewer channel frequenciesthan the other of the upstream data frame or the downstream data frame.

Example 21 includes the elements of example 19, including or omittingoptional elements, wherein: the mode selection circuitry is configuredto select a partial time division echo cancellation duplexing mode basedon the upstream data rate and the downstream data rate; and the frameconstruction circuitry is configured to, in response to selection of thepartial time division echo cancellation duplexing mode, construct anupstream data frame and a downstream data frame such that i) during afirst symbol position the upstream data frame and the downstream dataframe both include data encoded on particular channel frequencies andii) during a second symbol position one of the upstream data frame orthe downstream data frame, but not both, do not include data encoded onthe particular channel frequencies.

Example 22 includes the elements of example 19, including or omittingoptional elements, wherein: the mode selection circuitry is configuredto select a partial time division and frequency division echocancellation duplexing mode based on the upstream data rate and thedownstream data rate; and the frame construction circuitry is configuredto, in response to selection of the partial time division and frequencydivision echo cancellation duplexing mode, construct an upstream dataframe and a downstream data frame such that i) during a first symbolposition the upstream data frame includes data encoded on a first set ofchannel frequencies and the downstream data frame includes data encodedon a second set of channel frequencies that is different from the firstset; and ii) during a second symbol position the downstream data frameincludes data encoded on the first set of channel frequencies and theupstream data frame includes data encoded on a third set of channelfrequencies that is different from the first set.

Example 23 includes the elements of example 19, including or omittingoptional elements, wherein the mode selection circuitry is configuredto, based on the upstream data rate and the downstream data rate,instruct a transmitter transmitting one of the upstream data frame orthe downstream data frame to transmit at a reduced power during a leastone symbol position in the data frame as compared to a power level usedto transmit at other symbol positions in the same data frame.

Example 24 includes the elements of examples 19-23, including oromitting optional elements, wherein the data rate calculation circuitryis configured to: calculate an upstream data rate based on an upstreamSNR assuming full duplex transmission; and calculate a downstream datarate based on a downstream SNR assuming full duplex transmission; andthe mode selection circuitry is configured to select a mode based on acriteria that defines a target relationship between the upstream datarate and the downstream data rate.

Various illustrative logics, logical blocks, modules, and circuitsdescribed in connection with aspects disclosed herein can be implementedor performed with a general purpose processor, a digital signalprocessor (DSP), an application specific integrated circuit (ASIC), afield programmable gate array (FPGA) or other programmable logic device,discrete gate or transistor logic, discrete hardware components, or anycombination thereof designed to perform functions described herein. Ageneral-purpose processor can be a microprocessor, but, in thealternative, processor can be any conventional processor, controller,microcontroller, or state machine.

The above description of illustrated embodiments of the subjectdisclosure, including what is described in the Abstract, is not intendedto be exhaustive or to limit the disclosed embodiments to the preciseforms disclosed. While specific embodiments and examples are describedherein for illustrative purposes, various modifications are possiblethat are considered within the scope of such embodiments and examples,as those skilled in the relevant art can recognize.

In this regard, while the disclosed subject matter has been described inconnection with various embodiments and corresponding Figures, whereapplicable, it is to be understood that other similar embodiments can beused or modifications and additions can be made to the describedembodiments for performing the same, similar, alternative, or substitutefunction of the disclosed subject matter without deviating therefrom.Therefore, the disclosed subject matter should not be limited to anysingle embodiment described herein, but rather should be construed inbreadth and scope in accordance with the appended claims below.

In particular regard to the various functions performed by the abovedescribed components (assemblies, devices, circuits, systems, etc.), theterms (including a reference to a “means”) used to describe suchcomponents are intended to correspond, unless otherwise indicated, toany component or structure which performs the specified function of thedescribed component (e.g., that is functionally equivalent), even thoughnot structurally equivalent to the disclosed structure which performsthe function in the herein illustrated exemplary implementations of thedisclosure. In addition, while a particular feature may have beendisclosed with respect to only one of several implementations, suchfeature may be combined with one or more other features of the otherimplementations as may be desired and advantageous for any given orparticular application.

What is claimed is:
 1. A partial echo cancellation duplexing system,comprising: a channel estimation circuitry configured to: determine anupstream crosstalk effect for an upstream channel between a first deviceand a second device; and determine a downstream crosstalk effect for adownstream channel between the first device and the second device;wherein the upstream crosstalk effect, the downstream crosstalk effect,or both, includes near end crosstalk from a third device that isnon-co-located with respect to the first device and the second device;and a partial echo cancellation duplexing circuitry configured to adjusta data rate of an upstream transmission or downstream transmission basedon the upstream crosstalk effect and the downstream crosstalk effect,wherein the channel estimation circuitry is configured to determine theupstream crosstalk effect and the downstream crosstalk effect based on:transmissions of an upstream data frame and a downstream data frame,wherein one or both of the upstream data frame and the downstream dataframe include a synchronization symbol or a quiet symbol in a firstsymbol position; and measurement of one or more of a downstream channelsignal-to-noise ratio (SNR), an upstream channel SNR, a downstreamchannel far end crosstalk coupling, an upstream channel far endcrosstalk coupling, a downstream channel near end crosstalk coupling,and an upstream channel near end crosstalk during the first symbolposition.
 2. The partial echo cancellation duplexing system of claim 1,wherein the one or both of the upstream data frame and the downstreamdata frame include the synchronization symbol or the quiet symbol in thefirst symbol position and a second symbol position, wherein the channelestimation circuitry is configured to determine the upstream crosstalkeffect and the downstream crosstalk effect based on measurements of oneor more of a downstream channel SNR, a downstream channel far endcrosstalk coupling, and a downstream channel near end crosstalk couplingduring the first symbol position; and measurement of one or more of anupstream channel SNR, an upstream channel far end crosstalk coupling,and an upstream channel near end crosstalk coupling during the secondsymbol position.
 3. The partial echo cancellation duplexing system ofclaim 1, wherein both the upstream data frame and the downstream dataframe include a synchronization symbol in the first symbol position. 4.The partial echo cancellation duplexing system of claim 1, wherein oneof the upstream data frame and the downstream data frame includes asynchronization symbol in the first symbol position and the other of theupstream data frame and the downstream data frame includes a quietsymbol in the first symbol position.
 5. The partial echo cancellationduplexing system of claim 1, wherein the partial echo cancellationduplexing circuitry is configured to adjust the data rate byconstructing an upstream data frame and a downstream data frame suchthat during a least one symbol position the upstream data frame or thedownstream data frame or both includes data encoded on fewer channelfrequencies than the other symbol positions of the same upstream dataframe or the downstream data frame or both.
 6. The partial echocancellation duplexing system of claim 1, wherein the partial echocancellation duplexing circuitry is configured to adjust the data rateby constructing an upstream data frame and a downstream data frame suchthat i) during a first symbol position the upstream data frame and thedownstream data frame both include data encoded on particular channelfrequencies and ii) during a second symbol position one of the upstreamdata frame or the downstream data frame, but not both, do not includedata encoded on the particular channel frequencies.
 7. The partial echocancellation duplexing system of claim 1, wherein the partial echocancellation duplexing circuitry is configured to adjust the data rateby constructing an upstream data frame and a downstream data frame suchthat i) during a first symbol position the upstream data frame includesdata encoded on a first set of channel frequencies and the downstreamdata frame includes data encoded on a second set of channel frequenciesthat is different from the first set; and ii) during a second symbolposition the downstream data frame includes data encoded on the firstset of channel frequencies and the upstream data frame includes dataencoded on a third set of channel frequencies that is different from thefirst set.
 8. The partial echo cancellation duplexing system of claim 1,wherein the partial echo cancellation duplexing circuitry is configuredto adjust the data rate by: constructing an upstream data frame and adownstream data frame; and instructing a transmitter transmitting one ofthe upstream data frame or the downstream data frame to transmit at areduced power during a least one symbol position in the data frame ascompared to a power level used to transmit at other symbol positions inthe same data frame.
 9. The partial echo cancellation duplexing systemof claim 1, wherein the partial echo cancellation duplexing circuitry isconfigured to adjust the data rate by: calculating an upstream data ratebased on an upstream channel SNR assuming full duplex transmission;calculating a downstream data rate based on a downstream channel SNRassuming full duplex transmission; and adjusting the data rate based ona criteria that defines a target relationship between the upstream datarate and the downstream data rate.
 10. A method to transmit dataupstream between a first device and a second device and downstreambetween the second device and the first device, comprising: determiningan upstream crosstalk effect for an upstream channel; determining adownstream crosstalk effect for a downstream channel; wherein theupstream crosstalk effect, the downstream crosstalk effect, or both,includes near end crosstalk from a third device that is non-co-locatedwith respect to the first device and the second device; and based on theupstream crosstalk effect and the downstream crosstalk effect, adjustinga data rate of an upstream transmission or downstream transmission,wherein determining the upstream crosstalk effect and determining thedownstream crosstalk effect comprise: transmitting an upstream dataframe and a downstream data frame, wherein one or both of the upstreamdata frame and the downstream data frame include a synchronizationsymbol or a quiet symbol in a first symbol position; and measuring oneor more of a downstream channel signal-to-noise ratio (SNR), an upstreamchannel SNR, a downstream channel far end crosstalk coupling, anupstream channel far end crosstalk coupling, a downstream channel nearend crosstalk coupling, and an upstream channel near end crosstalkduring the first symbol position.
 11. The method of claim 10, whereinthe one or both of the upstream data frame and the downstream data frameinclude the synchronization symbol or the quiet symbol in the firstsymbol position and a second symbol position, wherein determining theupstream crosstalk effect and determining the downstream crosstalkeffect comprise measuring one or more of a downstream channel SNR,downstream channel far end crosstalk coupling, and downstream channelnear end crosstalk coupling during the first symbol position; andmeasuring one or more of an upstream channel SNR, upstream channel farend crosstalk coupling, and upstream channel near end crosstalk couplingduring the second symbol position.
 12. The method of claim 10, whereinadjusting the data rate comprises constructing an upstream data frameand a downstream data frame such that during a least one symbol positionthe upstream data frame or the downstream data frame includes dataencoded on fewer channel frequencies than the other of the upstream dataframe or the downstream data frame.
 13. The method of claim 10, whereinadjusting the data rate comprises constructing an upstream data frameand a downstream data frame such that i) during a first symbol positionthe upstream data frame and the downstream data frame both include dataencoded on particular channel frequencies and ii) during a second symbolposition one of the upstream data frame or the downstream data frame,but not both, do not include data encoded on the particular channelfrequencies.
 14. The method of claim 10, wherein adjusting the data ratecomprises constructing an upstream data frame and a downstream dataframe such that i) during a first symbol position the upstream dataframe includes data encoded on a first set of channel frequencies andthe downstream data frame includes data encoded on a second set ofchannel frequencies that is different from the first set; and ii) duringa second symbol position the downstream data frame includes data encodedon the first set of channel frequencies and the upstream data frameincludes data encoded on a third set of channel frequencies that isdifferent from the first set.
 15. The method of claim 10, whereinadjusting the data rate comprises: constructing an upstream data frameand a downstream data frame; and instructing a transmitter transmittingone of the upstream data frame or the downstream data frame to transmitat a reduced power during a least one symbol position in the data framesas compared to power used to transmit at other symbol positions in thedata frames.
 16. The method of claim 10, wherein adjusting the data ratecomprises: calculating an upstream data rate based on an upstreamchannel SNR assuming full duplex transmission; calculating a downstreamdata rate based on an downstream channel SNR assuming full duplextransmission; and adjusting the data rate based on a criteria thatdefines a target relationship between the upstream data rate and thedownstream data rate.